<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>新浪网</title>
    <style>
        .main {
            width: 800px;
            margin: auto;
        }

        img {
            width: 100%;
        }

        .adleft {
            width: 120px;
            height: 288px;
            position: fixed;
            top: 50%;
            margin-top: -144px;
            left: 0;
        }

        .adright {
            width: 120px;
            height: 288px;
            position: fixed;
            top: 50%;
            margin-top: -144px;
            right: 0;
        }

        .backtop {
            position: fixed;
            bottom: 5px;
            right: 0;
            width: 40px;
            height: 40px;
            background: url(./img/sprite_right.png) no-repeat gray -112px -296px;
        }

        .backtop:hover {
            background-position: -204px -112px;
        }
    </style>
</head>

<body>
    <a id="top"></a>
    <div class="main">
        <img src="./img/box.png">
    </div>
    <div class="adleft">
        <img src="./img/ad-l.png">
    </div>
    <div class="adright">
        <img src="./img/ad-r.png">
    </div>
    <a href="#top">
        <div class="backtop">
        </div>
    </a>
</body>

</html>